This invention to relates to franking of mail items with postage charge.
Known postage meters for franking mail items include accounting means to carry out accounting functions in respect of postage charges dispensed by the meter and a printer to print a franking impression on the each mail item to indicate that a postage charge has been applied to the mail item and has been levied against the user of the postage meter. Earlier postage meters incorporated a drum printer to print the franking impression. The drum printer comprises a rotatable print drum carrying a fixed printing die to print invariable parts of the impression and sets of print wheels which are set to print a required value of postage charge and the date on which the printing is effected. In more recent developments of postage meters the rotatable print drum has been replaced by electronic digital printing devices. These digital printing devices comprise means to print dots selectively in a plurality of positions in a column and the franking impression is printed in a succession of print cycles in each of which cycles the printing device prints dots in positions such as to build up the impression in a column-by-column manner. Digital printing devices proposed for this purpose include thermal printers and ink jet.